A disc segment adapted to be attached to other disc segments to form a disc assembly, the disc segment including an isosceles trapezoid frame. The frame comprises a left side rail and a right side rail, and a plurality of spaced apart parallel horizontally extending ribs connected between the side rails. The frame defines a first disc side and an opposite second disc side, each disc side including a corrugated left bottom clamp list adjacent the left side rail and supported by the ribs, and a corrugated right bottom clamp list adjacent the right side rail and supported by the ribs. Each disc side also includes a corrugated wire mesh supported by the left and right clamp lists, and supported by the frame ribs.